In my wiki I used #forminput several times for a longer period to pass values to new pages.

EXAMPLE:

{{#forminput:form=Dokument
|size= 110
|default value=Datei:Testdatei.pdf
|autocomplete on category= Dokument
|Dokument[Dokumenttyp]=Angeb
|Dokument[gehört zu Beschaffungsvorgang]={{FULLPAGENAMEE}}
|Dokument[Geschäftspartner]={{urlencode:AnyCompany Ltd}}
|AKS[UstNr]=01
}}

I cannot say from wich point of time #forminput runs into the following error

Error Message:
       An internal server error occurred. Please try again later.

This flaw has come with some Version after 5.x.

I found that this happens in any case when values are passed to a "multiple" form. In the example "AKS" is a multiple form within Form:Dokument. If I remove the line |AKS[..... from the #forminput tag all is fine.

When adding a "counter" to the string things change from case to case:

If the counter is 0

|AKS[0][UstNr]=01

the error does not occur but no data is transferred to the "multiple" form.

On any other counter the error occurs. like

|AKS[1][UstNr]=01
|AKS[2][UstNr]=01

This was already discussed on the mailing list semediawiki-user@lists.sourceforge.net